It is common knowledge that UNC is one of the very top programs in the nation. They have tons of research money and tuition is relatively cheap. I like that you start clinical experience within the first year, the facilities are great, patient base good, location nice. They have a very strong program with enthusiastic students and faculty. It is the closest in philosophy to Iowa, which I also loved. They seem to crank out very well educated and experienced students. Also, I did some shadowing with Gordon Christensen's son and he seemed to think UNC was about the best you could go.
On the other hand, I had pretty well decided I liked UNC so Maryland was no big excitement. They are getting a new school! I just wasn't as impressed with how they sold their program. I am looking to get straight into a GP out of school and a huge number of Maryland students do GPRs. Wondered if that was because they didn't feel prepared? Anyway, cost of living, tuition, etc. Both great schools. Being from NC you probably aren't as excited about your state school as the rest of us. I don't think you could go wrong with either. But, if you could pay less to get to a stronger program. . .go for it. Also, the strong research background gives many opportunities for funding, grants, etc.